Electrostatic system for treating liquids

ABSTRACT

An electrostatic system for treating liquid within a container includes a two wire, electrostatic field generator of improved construction having an enclosed two wire electrical supply and grounding provision, a concealed grounding connection, and an improved electrode construction to facilitate assembly and dissassembly thereof. The subject improved field generator may be used in an aerated circulation system to effectively moderate the rate of propagation of certain undesired bacterial cultures.

BACKGROUND OF THE INVENTION

This invention is directed to an improved electrostatic system fortreating liquids, and in particular, the provision of a protected, twowire system, including an improved electrostatic field generator.

In ARNESEN et al prior U.S. Pat. No. 4,545,887, there was provided animproved electrostatic field generator construction for use within atank or other enclosure, for purposes of ameliorating the occurrence ofscaling. The disclosed system also had the tendency to remove scale, ifit had formed within the water system, including a tank and piping. Theconstruction comprised a tube having protective end caps and a tensionrod joining the opposing ends in mechanically secured relation. Earlierarrangements are to be found in the following U.S. Pat. Nos.: 3,585,122,KING, issued June 15, 1971; 4,024,047, CLARK, issued May 17, 1977;4,073,712, MEANS, issued Feb. 14, 1978; 4,199,429, McMAHON, issued Apr.22, 1980, and in PCT Publication No. W080/00226, RABBIT, issued Feb. 21,1980.

While the use of an electrostatic field is well known in boiler andother industrial systems, for the prevention of scale formation and theactual reduction of deposited scale, surprising results have beenreported in regards to the use of applicant's electrostatic fieldgenerator in the reduction of bacterial counts in certain water systems.Thus, it has been found that installation and operation of anelectrostatic system incorporating the subject electrostatic fieldgenerator can drastically reduce the bacterial population within a givenwater system. It is further found that operation of the electrostaticsystem in a manner to effect bacterial control is not inimical to theanti-scaling function of the field generator.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is now provided animproved system, wherein the system wiring is improved, being lessvulnerable to damage. Also the grounding of the electrostatic fieldgenerator utilizes a concealed grounding wire to minimize the likelihoodof accidental or malicious interference, and the elimination ofconsequential electrical hazard. Furthermore, there is now provided afield generator construction of an enhanced type, capable ofwithstanding higher temperatures, and better suited for assembly anddisassembly, utilizing modular parts for more rapid construction andreconstruction.

In addition there is now provided an enhanced method of operation,including the steps of inserting the subject electrostatic fieldgenerator within a receptacle, to generate a predetermined electrostaticfield, circulating the liquid, generally water, through the so-generatedelectrostatic field, and oxygenating the circulating liquid, so as tomoderate the growth of a predetermined bacterial population within thesystem.

In the case of the above noted prior ARNESEN et al construction, thesystem circuit utilized a single wire high tension (HT) supply, with thebrass mounting boss of the field generator providing grounding contactwith the metal wall of the vessel in which the field generator wasmounted. An external electrical connection was provided to connect thewall of the vessel to ground. In the event of accidental disconnection,this constituted a potential hazard.

In the presently disclosed construction, a multi-wire circuit includesthe HT generator supply and also connects the mounting boss of the fieldgenerator by way of a grounding wire to the HT power supply.

This is of particular importance in that the occurrence of changinglocal conditions, relative to the electrical grounding of the vessel inwhich the field generator is mounted, cannot now create an electricallyhazardous condition. In the case of a return header pipe installationthe grounding connection now no longer requires the provision of agrounding clamp on the pipe. Such clamps are very vulnerable toaccidental, or unauthorized or malicious removal.

Furthermore, in the event of accidental damage to the insulation of theHT connection, the co-existence of a grounding wire with the HT lead,and within the same supply conduit, greatly increases the likelihoodthat any short circuit of the HT supply lead will result in transfer ofthe short circuit current directly back to the DC supply source throughthe grounding lead. This in turn diminishes the likelihood of thevoltage potential of the tank or other installation being raised aboveground value as a consequence of such a short circuit, while alsoenhancing the probability of the actuation of circuit protectiondevices, such as fuses or ground current protectors.

In addition to the foregoing improvements, the presently disclosedconstruction provides an electrostatic field generator of modularconstruction, having provision for making electrical HT and groundingconnections thereto by way of a suitable conduit, mechanically connectedto the field generator structure, and with concealed internalconnections.

There are further provided certain embodiments incorporating improvedconstruction of the distal end of the field generator, having a closurebushing secured to the end of the tubular portion, and a non-conductiveinsulating sleeve extending thereover, in protective and insulatingrelation.

In one such embodiment there is illustrated a sleeve of material such aspolytetrafluoroethylene (PTFE), which is heat shrunk into place.

In a second such embodiment a PTFE or other similar end cap is welded toa PTFE sleeve, and a second sleeve shrunk thereover in sealingprotective relation.

It will be understood that the closure bushing may be of conducting orof non-conducting material, for such embodiments.

In addition to the improved apparatus herein disclosed, there is nowprovided a method of operating the apparatus comprising the steps ofenergizing the field generator at a predetermined voltage so as togenerate an electrostatic field, and circulating the liquid through thethus-generated electrostatic field. In addition, operation of the systemso as increase oxygenation of the liquid, preferably through the mediumof the system pump, further extends the beneficial effects of thesystem.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the invention are described, reference being madeto the drawings, wherein;

FIG. 1 is a schematic view of a typical liquid system which utilizes anelectrostatic field generator according to the present invention.

FIG. 2 is a side view, in diametrical section of the improvedelectrostatic field generator;

FIG. 3 is an exploded view of the components of the mounting boss of thesubject field generator;

FIG. 4 is a cross sectional view taken at 4--4 of FIG. 2;

FIG. 5 is a side view in diametrical section of the distal end ofanother embodiment of the improved field generator;

FIG. 6 is a like view of a still further embodiment;

FIG. 7 shows a closed loop heating system incorporating the fieldgenerator; and

FIG. 8 shows a cooling tower and evaporative condenser systemincorporating the field generator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a typical system 10 is shown schematically, ininstalled relation to a tank 12. The tank 12 has connections 14 and 16for the transfer of liquid therethrough. A pump 17 may be used tocirculate the liquid to the tank 12, and may have a valve 19 to controlinduced air flow. In any event, the system 10 includes some form ofvessel or tank 12, into which the field generator protrudes. It may alsobe used in a header such as may be associated with a boiler.

The system 10 further comprises a power supply 18, which includes ahousing 20 provided with a grounding connection 22 and a supplyconnection 24 operating at normal domestic supply voltage of 110 or 220volts as the case may be.

A reinforced metallic cable cover or rigid duct 26, illustrated as theformer, connects the HT supply 18 to the field generator 30. The HTsupply comprises an insulated HT lead 23 operating in the direct currentvoltage range of about 6000 volts, and a grounding connection 22.

In certain system installations, such as when the liquid in the systemis water which may be used for irrigation purposes in commercialgreenhouses and the like, opening of valve 19 permits a controlled flowof air in induced relation into the eye of the pump 19, so as tooxygenate the system.

Referring to FIG. 2, the field generator 30 has an portion 32, anelectrically conductive tie rod 34 and spring contact spider 34, and athreaded bushing 36 by which the field generator 30 is mounted. Theremote (distal) end of electrode portion 32 comprises a non-conductivemember 29, over which an electrically conductive member--usually analuminum tube 31--extends. A bushing 33 is positioned in sealingrelation over the distal end of the tube 31, and is sealed thereto byO-rings 35. An air vent passage 37 connects the enclosed space 39 withinbushing 33 to the interior 41 of the portion 32. In addition tofacilitating assembly and removal of the bushing 33 by permitting airflow from within the interior of the bushing 33 to the interior of thetube 31 as the bushing is advanced over the end of the tube, this vent37 also reduces the loading on the O-rings 35, while also diminishingthose variations in axial forces brought about by pressure changes dueto variations in system ambient temperature.

Referring also to FIG. 3, the field generator 30 includes proximal endbushing 36, with an internal insulating bushing 46 having an axiallyextending recess 48 therein to receive a tensioning nut 50, and theproximal end 54 of rod 34. The proximal end 54 of rod 34 has a threadedhole therein by which screw 56 secures lug end 58 of HT lead 23. Thebushing 46 requires to be substantially temperature insensitive, and toresist compressive loading thereon, and is preferably of PTFE, either aglass loaded or pure form such as TEFLON®.

A cylindrical cover 60 is secured by cap screws 62 to the body portion36, an elastomeric seal 64 being interposed therebetween. The lug end 69of ground connection 29 is secured by screw 71 to a recessed faceportion 74 of the cover 60, by way of a threaded hole 75.

An electrical conduit connector 76 is threadedly secured to the cover60, whereby the duct or cover 26 is securely connected to cover 60,thereby effecting protection to grounding connection 29 and HT lead 23,within a common path.

As noted above, and referring to FIGS. 2 and 4, a vent passage 37extends longitudinally through the stepped end plug 29. The reduceddiameter portion of the plug 29 extends within the distal end of themetal pipe 31, over which a PTFE sleeve is shrunk in insulative andprotective relation. The vent passage 37 serves to equalize the internalair pressure between the interior of pipe 31 and the interior of distalend member 33.

Referring to FIGS. 5 and 6, there are illustrated two distal endconstructions 81 and 83 respectively, having a tube portion 32, and anend bushing 82 or 84 in inserted relation therein, secured by tensionrod 34.

A PTFE sleeve 85 is shrunk over the FIG. 5 embodiment.

In the case of the FIG. 6 embodiment, a PTFE end cap 87 is welded at 88to a sleeve 89, and has a second PTFE sleeve 90 in partial overlyingrelation, and being heat shrunk in protective sealing engagementtherewith. The end bushing 84, may be profiled in a suitable manner,such as that illustrated, in order to facilitate the welding of the endcap 87 to the sleeve 89. The extent of overlap of the PTFE sleeve 90past the weld zone 88 affords additional protection to the weld zone 88.

The provision of a pair of PTFE sleeves in overlying shrunk-on relationprovides additional protection from hazards such as pin holeperforations.

Referring to FIGS. 7 and 8, FIG. 7 shows a schematic arrangement of aportion of a closed loop heating system 170. The system 170 has a hotwater boiler 172 to which a return line 174 connects, by way of header176.

A field generator 30 in accordance with the present invention is mountedwithin header 176 in the fashion of a rod immersion heater.

A make-up water line 178, complete with a make-up water control valve179, connected in parallel with expansion tank 180. The line 178connects by line 181 with the outlet line 182 from the boiler 172, whichis connected to the inlet of circulation pump 184 for delivering hotwater to the system being served.

Turning to FIG. 8, which shows a closed loop chiller circuit 190incorporating a cooling tower/evaporative condenser 192. The sump 194 ofthe arrangement has a field generator 30 inserted therein. The sump 194connects by way of pump 196 with a chiller/compressor 198, which has areturn line 199 back to the tower 192.

The installations of FIGS. 7 and 8 illustrate schematically certain ofthe types of installation on which the effects of electrostatic fieldgenerators were tried, on a test basis.

From observed tests carried out on a number of test installations, eachincorporating a field generator, the following reports emerged:

(1) A field generator was used for a period of months in an installationincorporating a cooling tower in a circuit such as that shown in FIG. 8.All chemical water treatments were discontinued over the life of thetests. An inspection of the cooling tower and the tubes of the condenserand chiller, showed that they had become scale-free, and they alsoshowed no sign of the presence of any algae.

(2) A four month comparative test was carried out on another system suchas that illustrated in FIG. 8, comprising a 150 ton cooling tower incombination with a 200 ton chiller, the use of chemical water treatmentswas discontinued prior to the test. The test showed an absence of scaleformation or biological fouling to the same extent as were observed in anumber of corresponding control units which relied upon chemicaltreatment of the water. Moreover, at the end of the test period, it wasnoted that no anodic film was present in the tower and chiller circuitincorporating the field generator in its circuit.

(3) A two month test on a humidification system was carried out. Priorto the test, the 250 gallons per minute system had operated on week daysand was shut down automatically on weekends. Chemical additive in theamount of one pint of liquid phosphate every two weeks had been totallyunable to control a weekend bacteria count build up which wassufficiently extensive that each Monday the odor therefrom was"unbearable". The system was flushed down, chemical additives werediscontinued and a field generator was installed.

The initial bacteriological count at commencement of the test was 8900parts per milliliter (p.p.m.); after six days the count had climbed to10,000 p.p.m.; and after a further thirteen days the count climbed to40,000 p.p.m. However, after a further fourteen days, the count droppedto 3,400 p.p.m.; and a further fourteen days later the count reached alow of 1,200 p.p.m. Previously, with the system relying upon thephosphate treatments, the deposition of hard water scale on thehumidifier would reduce air flow by 50% by season's end. After using thefield generator for the season, the system was so clean that highairflows were maintained and no acid cleaning was required, as wouldnormally have been the case.

The disclosed embodiment of a field generator for electrostatictreatment of a liquid is illustrated as being mounted within a tank(FIG. 1), a flow header (FIG. 7), and a sump (FIG. 8), with appropriatereferences being made thereto. However, it will be understood that thesubject system is also applicable to a header or other liquid containingcomponents of a system.

I claim:
 1. An electrostatic field generator system adapted for use witha liquid-containing receptacle, said system comprisinga. a source ofdirect current high voltage having a high voltage connection and agrounding connection; b. an electrode adapted for mounting through anopening in a wall of the receptacle and comprisingan elongatedconductive tubular member having a proximal end and a distal end, asleeve fitted in insulative and protective relation over said tubularmember, a distal bushing positioned in sealing relation at the distalend of said tubular member, a conductive proximal bushing having ahollow interior and two ends, the first end being positioned over andengaging said tubular member in the region adjacent the proximal end andthe second end extending past the proximal end of the tubular member,said proximal bushing including means for mounting the electrode suchthat said proximal bushing is in electrical contact with the receptacleand said tubular member extends into the recepticle, a high voltageterminal located within the interior of said proximal bushing, means forconnecting said high voltage terminal to the interior of said tubularmember, insulating means within the interior of said proximal bushing toinsulate said proximal bushing from said high voltage terminal, aconductive closure member having an inner surface disengagably engagablewith and positioned to cover the second end of said proximal bushing, agrounding terminal located on the inner surface of said closure member,said closure member being engaged by means of a conductive engagingmember extending between the closure member and the proximal bushing toprovide electrical contact of the closure member and hence the groundingterminal with said proximal bushing; and c. an insulated high tensionlead connecting said high voltage connection of the high voltage sourceto said high voltage terminal and a grounding lead connecting saidgrounding connection to said grounding terminal,whereby the groundedcondition of said proximal bushing is substantially independent of theelectrical potential acting on said receptacle.
 2. The electrostaticfield generator system of claim 1, wherein said insulating meanscomprises a modular preformed bushing located in close fitting relationwithin said proximal bushing.
 3. The electrostatic field generatorsystem of claim 1, wherein said high voltage lead and said groundinglead are located within a common mechanically protected passage whichconnects said voltage source to said electrode.
 4. The electrostaticfield generator system of claim 3, wherein said grounding lead isunsheathed.
 5. The electrostatic field generator system of claim 1wherein said distal bushing extends over the distal end of said tubularmember, and wherein the electrode further comprises a nonconductive endplug located within the tubular member in the region extending inwardfrom the distal end, said non-conductive member having a vent passageextending longitudinally therethrough.
 6. The electrostatic fieldgenerator system of claim 1 wherein said distal bushing is partiallyfitted within the distal end of said tubular member, and a dielectriclayer is provided in insulating relation over said distal bushing. 7.The electrostatic field generator system of claim 1 wherein said distalbushing is partially fitted within the distal end of said tubularmember, an insulative end cap is provided over the distal bushing and asecond sleeve is provided in partial overlying relation thereto.